Superfluidity in a quasi-one-dimensional atomic Bose-Einstein condensate

B Kh Turmanov, F. Kh. Abdullaev, F.Z. Isakov

Chao Feng, Matthew J. Davis

Luca Salasnich

We find exact solutions of the hydrodynamic equations of a dilute and ultracold atomic Bose-Einstein condensate confined in the cylindric radial direction by a harmonic potential and freely travelling in the longitudinal axial direction. The dynamics of these solutions, which generalize the ones obtained for a purely one-dimensional superfluid in the regime of quasi-condensation, gives rise to a shock-wave front whose period of formation is analytically estimated. We suggest that these shock waves can be experimentally produced by engineering the initial density and phase of an atomic Bose-Einstein condensate.

Alexey V. Yulin, Yu. V. Bludov, V. V. Konotop +2 more

Superfluid properties of Bose-Einstein condensates (BEC) in toroidal quasi-one-dimensional traps are investigated in the presence of periodic scattering length modulations along the ring. The existence of several types of stable periodic waves, ranging from almost uniform to very fragmented chains of weakly interacting and equally spaced solitons, is demonstrated. We show that these waves may support persistent atomic currents and sound waves with spectra of Bogoliubov type. Fragmented condensates can be viewed as arrays of Josephson junctions and the current as a BEC manifestation of the dc-Josephson effect. The influence of linear defects on BEC superfluidity has been also investigated. We found that for subcritical velocities, linear defects that are static with respect to the lattice (while the condensate moves in respect to both the optical lattice and the defect) preserve the BEC superfluidity.

Wolfgang Ketterle

Yi Zheng

Several aspects of superfluidity in an atomic Bose-Einstein Condensate are studied in a torus-type quasi-1D model. The critical velocity of the superfluid in this quasi-1D model is found to differ from the conventional concept of the limit of velocity for frictionless flow. This result is one of the unique features of the quasi-1D system. For a generalized discrete quasi-1D model, the stability of Bloch oscillations is studied. The quasi-particle spectrum of small oscillations is analyzed, which in turn gives the phase diagram of the stable-unstable region. The results are in good agreement with a recent experimental observation. Last, we consider an experiment proposal where a phase-imprinting technique is used to generate superfluid flow with fixed momentum or a vortex in atomic BEC. Our study shows that because of backflow generated by part of the imprinting potential, phase imprinting is not an ideal tool to generate a single-momentum superflow or single vortex. ^